/*-
 *  * Copyright 2016 Skymind, Inc.
 *  *
 *  *    Licensed under the Apache License, Version 2.0 (the "License");
 *  *    you may not use this file except in compliance with the License.
 *  *    You may obtain a copy of the License at
 *  *
 *  *        http://www.apache.org/licenses/LICENSE-2.0
 *  *
 *  *    Unless required by applicable law or agreed to in writing, software
 *  *    distributed under the License is distributed on an "AS IS" BASIS,
 *  *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  *    See the License for the specific language governing permissions and
 *  *    limitations under the License.
 */

package org.datavec.api.writable;


import org.datavec.api.io.BinaryComparable;
import org.datavec.api.io.WritableComparable;
import org.datavec.api.io.WritableComparator;
import org.datavec.api.io.WritableUtils;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.*;
import java.text.CharacterIterator;
import java.text.StringCharacterIterator;



/** This class stores text using standard UTF8 encoding.  It provides methods
 * to serialize, deserialize, and compare texts at byte level.  The type of
 * length is integer and is serialized using zero-compressed format.  <p>In
 * addition, it provides methods for string traversal without converting the
 * byte array to a string.  <p>Also includes utilities for
 * serializing/deserialing a string, coding/decoding a string, checking if a
 * byte array contains valid UTF8 code, calculating the length of an encoded
 * string.
 */
public class Text extends BinaryComparable implements WritableComparable<BinaryComparable> {

    private static ThreadLocal<CharsetEncoder> ENCODER_FACTORY = new ThreadLocal<CharsetEncoder>() {
        protected CharsetEncoder initialValue() {
            return Charset.forName("UTF-8").newEncoder().onMalformedInput(CodingErrorAction.REPORT)
                            .onUnmappableCharacter(CodingErrorAction.REPORT);
        }
    };

    private static ThreadLocal<CharsetDecoder> DECODER_FACTORY = new ThreadLocal<CharsetDecoder>() {
        protected CharsetDecoder initialValue() {
            return Charset.forName("UTF-8").newDecoder().onMalformedInput(CodingErrorAction.REPORT)
                            .onUnmappableCharacter(CodingErrorAction.REPORT);
        }
    };

    private static final byte[] EMPTY_BYTES = new byte[0];

    private byte[] bytes;
    private int length;

    public Text() {
        bytes = EMPTY_BYTES;
    }

    /** Construct from a string.
     */
    public Text(String string) {
        set(string);
    }

    /** Construct from another text. */
    public Text(Text utf8) {
        set(utf8);
    }

    /** Construct from a byte array.
     */
    public Text(byte[] utf8) {
        set(utf8);
    }

    /**
     * Returns the raw bytes; however, only data up to {@link #getLength()} is
     * valid.
     */
    public byte[] getBytes() {
        return bytes;
    }

    /** Returns the number of bytes in the byte array */
    public int getLength() {
        return length;
    }

    /**
     * Returns the Unicode Scalar Value (32-bit integer value)
     * for the character at <code>position</code>. Note that this
     * method avoids using the converter or doing String instatiation
     * @return the Unicode scalar value at position or -1
     *          if the position is invalid or points to a
     *          trailing byte
     */
    public int charAt(int position) {
        if (position > this.length)
            return -1; // too long
        if (position < 0)
            return -1; // duh.

        ByteBuffer bb = (ByteBuffer) ByteBuffer.wrap(bytes).position(position);
        return bytesToCodePoint(bb.slice());
    }

    public int find(String what) {
        return find(what, 0);
    }

    /**
     * Finds any occurence of <code>what</code> in the backing
     * buffer, starting as position <code>start</code>. The starting
     * position is measured in bytes and the return value is in
     * terms of byte position in the buffer. The backing buffer is
     * not converted to a string for this operation.
     * @return byte position of the first occurence of the search
     *         string in the UTF-8 buffer or -1 if not found
     */
    public int find(String what, int start) {
        try {
            ByteBuffer src = ByteBuffer.wrap(this.bytes, 0, this.length);
            ByteBuffer tgt = encode(what);
            byte b = tgt.get();
            src.position(start);

            while (src.hasRemaining()) {
                if (b == src.get()) { // matching first byte
                    src.mark(); // save position in loop
                    tgt.mark(); // save position in target
                    boolean found = true;
                    int pos = src.position() - 1;
                    while (tgt.hasRemaining()) {
                        if (!src.hasRemaining()) { // src expired first
                            tgt.reset();
                            src.reset();
                            found = false;
                            break;
                        }
                        if (!(tgt.get() == src.get())) {
                            tgt.reset();
                            src.reset();
                            found = false;
                            break; // no match
                        }
                    }
                    if (found)
                        return pos;
                }
            }
            return -1; // not found
        } catch (CharacterCodingException e) {
            // can't get here
            e.printStackTrace();
            return -1;
        }
    }

    /** Set to contain the contents of a string.
     */
    public void set(String string) {
        try {
            ByteBuffer bb = encode(string, true);
            bytes = bb.array();
            length = bb.limit();
        } catch (CharacterCodingException e) {
            throw new RuntimeException("Should not have happened " + e.toString());
        }
    }

    /** Set to a utf8 byte array
     */
    public void set(byte[] utf8) {
        set(utf8, 0, utf8.length);
    }

    /** copy a text. */
    public void set(Text other) {
        set(other.getBytes(), 0, other.getLength());
    }

    /**
     * Set the Text to range of bytes
     * @param utf8 the data to copy from
     * @param start the first position of the new string
     * @param len the number of bytes of the new string
     */
    public void set(byte[] utf8, int start, int len) {
        setCapacity(len, false);
        System.arraycopy(utf8, start, bytes, 0, len);
        this.length = len;
    }

    /**
     * Append a range of bytes to the end of the given text
     * @param utf8 the data to copy from
     * @param start the first position to append from utf8
     * @param len the number of bytes to append
     */
    public void append(byte[] utf8, int start, int len) {
        setCapacity(length + len, true);
        System.arraycopy(utf8, start, bytes, length, len);
        length += len;
    }

    /**
     * Clear the string to empty.
     */
    public void clear() {
        length = 0;
    }

    /*
     * Sets the capacity of this Text object to <em>at least</em>
     * <code>len</code> bytes. If the current buffer is longer,
     * then the capacity and existing content of the buffer are
     * unchanged. If <code>len</code> is larger
     * than the current capacity, the Text object's capacity is
     * increased to match.
     * @param len the number of bytes we need
     * @param keepData should the old data be kept
     */
    private void setCapacity(int len, boolean keepData) {
        if (bytes == null || bytes.length < len) {
            byte[] newBytes = new byte[len];
            if (bytes != null && keepData) {
                System.arraycopy(bytes, 0, newBytes, 0, length);
            }
            bytes = newBytes;
        }
    }

    /**
     * Convert text back to string
     * @see java.lang.Object#toString()
     */
    public String toString() {
        try {
            return decode(bytes, 0, length);
        } catch (CharacterCodingException e) {
            throw new RuntimeException("Should not have happened " + e.toString());
        }
    }

    /** deserialize
     */
    public void readFields(DataInput in) throws IOException {
        int newLength = WritableUtils.readVInt(in);
        setCapacity(newLength, false);
        in.readFully(bytes, 0, newLength);
        length = newLength;
    }

    @Override
    public void writeType(DataOutput out) throws IOException {
        out.writeShort(WritableType.Text.typeIdx());
    }

    /** Skips over one Text in the input. */
    public static void skip(DataInput in) throws IOException {
        int length = WritableUtils.readVInt(in);
        WritableUtils.skipFully(in, length);
    }

    /** serialize
     * write this object to out
     * length uses zero-compressed encoding
     * @see Writable#write(DataOutput)
     */
    public void write(DataOutput out) throws IOException {
        WritableUtils.writeVInt(out, length);
        out.write(bytes, 0, length);
    }

    /** Returns true iff <code>o</code> is a Text with the same contents.  */
    public boolean equals(Object o) {
        return o instanceof Text && super.equals(o);
    }

    public int hashCode() {
        return super.hashCode();
    }

    /** A WritableComparator optimized for Text keys. */
    public static class Comparator extends WritableComparator {
        public Comparator() {
            super(Text.class);
        }

        public int compare(byte[] b1, int s1, int l1, byte[] b2, int s2, int l2) {
            int n1 = WritableUtils.decodeVIntSize(b1[s1]);
            int n2 = WritableUtils.decodeVIntSize(b2[s2]);
            return compareBytes(b1, s1 + n1, l1 - n1, b2, s2 + n2, l2 - n2);
        }
    }

    static {
        // register this comparator
        WritableComparator.define(Text.class, new Comparator());
    }

    /// STATIC UTILITIES FROM HERE DOWN
    /**
     * Converts the provided byte array to a String using the
     * UTF-8 encoding. If the input is malformed,
     * replace by a default value.
     */
    public static String decode(byte[] utf8) throws CharacterCodingException {
        return decode(ByteBuffer.wrap(utf8), true);
    }

    public static String decode(byte[] utf8, int start, int length) throws CharacterCodingException {
        return decode(ByteBuffer.wrap(utf8, start, length), true);
    }

    /**
     * Converts the provided byte array to a String using the
     * UTF-8 encoding. If <code>replace</code> is true, then
     * malformed input is replaced with the
     * substitution character, which is U+FFFD. Otherwise the
     * method throws a MalformedInputException.
     */
    public static String decode(byte[] utf8, int start, int length, boolean replace) throws CharacterCodingException {
        return decode(ByteBuffer.wrap(utf8, start, length), replace);
    }

    private static String decode(ByteBuffer utf8, boolean replace) throws CharacterCodingException {
        CharsetDecoder decoder = DECODER_FACTORY.get();
        if (replace) {
            decoder.onMalformedInput(java.nio.charset.CodingErrorAction.REPLACE);
            decoder.onUnmappableCharacter(CodingErrorAction.REPLACE);
        }
        String str = decoder.decode(utf8).toString();
        // set decoder back to its default value: REPORT
        if (replace) {
            decoder.onMalformedInput(CodingErrorAction.REPORT);
            decoder.onUnmappableCharacter(CodingErrorAction.REPORT);
        }
        return str;
    }

    /**
     * Converts the provided String to bytes using the
     * UTF-8 encoding. If the input is malformed,
     * invalid chars are replaced by a default value.
     * @return ByteBuffer: bytes stores at ByteBuffer.array()
     *                     and length is ByteBuffer.limit()
     */

    public static ByteBuffer encode(String string) throws CharacterCodingException {
        return encode(string, true);
    }

    /**
     * Converts the provided String to bytes using the
     * UTF-8 encoding. If <code>replace</code> is true, then
     * malformed input is replaced with the
     * substitution character, which is U+FFFD. Otherwise the
     * method throws a MalformedInputException.
     * @return ByteBuffer: bytes stores at ByteBuffer.array()
     *                     and length is ByteBuffer.limit()
     */
    public static ByteBuffer encode(String string, boolean replace) throws CharacterCodingException {
        CharsetEncoder encoder = ENCODER_FACTORY.get();
        if (replace) {
            encoder.onMalformedInput(CodingErrorAction.REPLACE);
            encoder.onUnmappableCharacter(CodingErrorAction.REPLACE);
        }
        ByteBuffer bytes = encoder.encode(CharBuffer.wrap(string.toCharArray()));
        if (replace) {
            encoder.onMalformedInput(CodingErrorAction.REPORT);
            encoder.onUnmappableCharacter(CodingErrorAction.REPORT);
        }
        return bytes;
    }

    /** Read a UTF8 encoded string from in
     */
    public static String readString(DataInput in) throws IOException {
        int length = WritableUtils.readVInt(in);
        byte[] bytes = new byte[length];
        in.readFully(bytes, 0, length);
        return decode(bytes);
    }

    /** Write a UTF8 encoded string to out
     */
    public static int writeString(DataOutput out, String s) throws IOException {
        ByteBuffer bytes = encode(s);
        int length = bytes.limit();
        WritableUtils.writeVInt(out, length);
        out.write(bytes.array(), 0, length);
        return length;
    }

    ////// states for validateUTF8

    private static final int LEAD_BYTE = 0;

    private static final int TRAIL_BYTE_1 = 1;

    private static final int TRAIL_BYTE = 2;

    /**
     * Check if a byte array contains valid utf-8
     * @param utf8 byte array
     * @throws MalformedInputException if the byte array contains invalid utf-8
     */
    public static void validateUTF8(byte[] utf8) throws MalformedInputException {
        validateUTF8(utf8, 0, utf8.length);
    }

    /**
     * Check to see if a byte array is valid utf-8
     * @param utf8 the array of bytes
     * @param start the offset of the first byte in the array
     * @param len the length of the byte sequence
     * @throws MalformedInputException if the byte array contains invalid bytes
     */
    public static void validateUTF8(byte[] utf8, int start, int len) throws MalformedInputException {
        int count = start;
        int leadByte = 0;
        int length = 0;
        int state = LEAD_BYTE;
        while (count < start + len) {
            int aByte = ((int) utf8[count] & 0xFF);

            switch (state) {
                case LEAD_BYTE:
                    leadByte = aByte;
                    length = bytesFromUTF8[aByte];

                    switch (length) {
                        case 0: // check for ASCII
                            if (leadByte > 0x7F)
                                throw new MalformedInputException(count);
                            break;
                        case 1:
                            if (leadByte < 0xC2 || leadByte > 0xDF)
                                throw new MalformedInputException(count);
                            state = TRAIL_BYTE_1;
                            break;
                        case 2:
                            if (leadByte < 0xE0 || leadByte > 0xEF)
                                throw new MalformedInputException(count);
                            state = TRAIL_BYTE_1;
                            break;
                        case 3:
                            if (leadByte < 0xF0 || leadByte > 0xF4)
                                throw new MalformedInputException(count);
                            state = TRAIL_BYTE_1;
                            break;
                        default:
                            // too long! Longest valid UTF-8 is 4 bytes (lead + three)
                            // or if < 0 we got a trail byte in the lead byte position
                            throw new MalformedInputException(count);
                    } // switch (length)
                    break;

                case TRAIL_BYTE_1:
                    if (leadByte == 0xF0 && aByte < 0x90)
                        throw new MalformedInputException(count);
                    if (leadByte == 0xF4 && aByte > 0x8F)
                        throw new MalformedInputException(count);
                    if (leadByte == 0xE0 && aByte < 0xA0)
                        throw new MalformedInputException(count);
                    if (leadByte == 0xED && aByte > 0x9F)
                        throw new MalformedInputException(count);
                    // falls through to regular trail-byte test!!
                case TRAIL_BYTE:
                    if (aByte < 0x80 || aByte > 0xBF)
                        throw new MalformedInputException(count);
                    if (--length == 0) {
                        state = LEAD_BYTE;
                    } else {
                        state = TRAIL_BYTE;
                    }
                    break;
            } // switch (state)
            count++;
        }
    }

    /**
     * Magic numbers for UTF-8. These are the number of bytes
     * that <em>follow</em> a given lead byte. Trailing bytes
     * have the value -1. The values 4 and 5 are presented in
     * this table, even though valid UTF-8 cannot include the
     * five and six byte sequences.
     */
    static final int[] bytesFromUTF8 = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
                    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
                    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
                    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
                    0, 0,
                    // trail bytes
                    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
                    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
                    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
                    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
                    3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5};

    /**
     * Returns the next code point at the current position in
     * the buffer. The buffer's position will be incremented.
     * Any mark set on this buffer will be changed by this method!
     */
    public static int bytesToCodePoint(ByteBuffer bytes) {
        bytes.mark();
        byte b = bytes.get();
        bytes.reset();
        int extraBytesToRead = bytesFromUTF8[(b & 0xFF)];
        if (extraBytesToRead < 0)
            return -1; // trailing byte!
        int ch = 0;

        switch (extraBytesToRead) {
            case 5:
                ch += (bytes.get() & 0xFF);
                ch <<= 6; /* remember, illegal UTF-8 */
            case 4:
                ch += (bytes.get() & 0xFF);
                ch <<= 6; /* remember, illegal UTF-8 */
            case 3:
                ch += (bytes.get() & 0xFF);
                ch <<= 6;
            case 2:
                ch += (bytes.get() & 0xFF);
                ch <<= 6;
            case 1:
                ch += (bytes.get() & 0xFF);
                ch <<= 6;
            case 0:
                ch += (bytes.get() & 0xFF);
        }
        ch -= offsetsFromUTF8[extraBytesToRead];

        return ch;
    }


    static final int offsetsFromUTF8[] = {0x00000000, 0x00003080, 0x000E2080, 0x03C82080, 0xFA082080, 0x82082080};

    /**
     * For the given string, returns the number of UTF-8 bytes
     * required to encode the string.
     * @param string text to encode
     * @return number of UTF-8 bytes required to encode
     */
    public static int utf8Length(String string) {
        CharacterIterator iter = new StringCharacterIterator(string);
        char ch = iter.first();
        int size = 0;
        while (ch != CharacterIterator.DONE) {
            if ((ch >= 0xD800) && (ch < 0xDC00)) {
                // surrogate pair?
                char trail = iter.next();
                if ((trail > 0xDBFF) && (trail < 0xE000)) {
                    // valid pair
                    size += 4;
                } else {
                    // invalid pair
                    size += 3;
                    iter.previous(); // rewind one
                }
            } else if (ch < 0x80) {
                size++;
            } else if (ch < 0x800) {
                size += 2;
            } else {
                // ch < 0x10000, that is, the largest char value
                size += 3;
            }
            ch = iter.next();
        }
        return size;
    }


    @Override
    public double toDouble() {
        if(toString().startsWith("0x"))
            return Long.decode(toString());

        return Double.parseDouble(toString());
    }

    @Override
    public float toFloat() {
        if(toString().startsWith("0x"))
            return Integer.decode(toString());
        return Float.parseFloat(toString());
    }

    @Override
    public int toInt() {
        if(toString().startsWith("0x"))
            return Integer.decode(toString());

        return Integer.parseInt(toString());
    }

    @Override
    public long toLong() {
        if(toString().startsWith("0x"))
            return Long.decode(toString());

        return Long.parseLong(toString());
    }

    @Override
    public WritableType getType() {
        return WritableType.Text;
    }
}
